Since the disclosure of organic light-emitting diodes (OLEDs), OLEDs have showed great potential in applications of optoelectronic devices (such as flat-panel displays and general lighting) because of the diversity in organic synthesis, relative low manufacturing costs, and excellent optical and electronic properties of organic/polymeric semiconductive materials.
To develop high-efficiency OLED devices, it is critical to inject electrons and holes from cathode and anode, repectively. Therefore, efficient OLED devices usually adopt a multi-layer device structure which comprises one or more hole-transport/injection layers, or electron-transport/injection layers, in addition to the light-emitting layer. Accordingly, in addition to developement of excellent light-emitting materials, the development of excellent electron-transport/injection materials and hole-transport/injection materials is also critical for obtaining high-efficiency OLEDs (J Mater Chem, 2008, 18: 4495-4509; Acc Chem Res, 2005, 38: 632-643; Adv Mater, 2007, 19: 810-814).
It is easy to obtain multi-layer and complex high-efficiency OLEDs by vacuum evaporation, but it is difficult to realize large-scale application due to the expensive, time-consuming and wasteful materials. In contrast, solution processing OLEDs may be advantageously widely used in the preparation of large-area flexible devices with low-cost ink jet printing, printing, and other solution processs, and therefore are promising in a wide range of applications and great commercial value. As typical organic photoelectric materials have similar solubility, that is, organic/polymer light-emitting materials, hole-injection/transport materials, electronic injection/transport materials have good solubility in solvents such as toluene, chloroform, chlorobenzene, o-dichlorobenzene, o-xylene and tetrahydrofuran, therefore, there are problems of miscibility and erosion of interfaces when using the solution process to prepare multi-layer, complex OLEDs. For example, when preparing polymers or small-molecule light-emitting layers using solution process, the solvent used may dissolve the underlying hole-transport layer, causing problems such as miscibility and erosion of interfaces (J Mater Chem, 2008, 18: 4495-4509; Chem Soc Rev, 2010, 39: 2500-2521).
When conventional crosslinking groups, such as perfluorocyclobutane, styrene, oxetane, siloxane, acrylate and benzocyclobutene, are used in modification of conjugated polymers, cross linking reaction of the crosslinking groups perfluorocyclobutane (Adv. Funct. Mater., 2002, 12, 745), styrene (Adv. Mater., 2007, 19, 300), oxetane (Nature, 2003, 421, 829.), siloxane (Acc. Chem. Res., 2005, 38, 632), acrylate (Chem. Mater., 2003, 15, 1491), and benzocyclobutene (Chem. Mater., 2007, 19, 4827.) can induced under conditions such as illumination, heating, etc, to form an insoluble and infusible film of interpenetrating polymer network with excellent solvent resistance so that the problems such as miscibility and erosion of interfaces are prevented (TW201406810A, U.S. Pat. No. 7,592,414B2).
However, the performance of solution-process OLEDs based on the cross-linked polymer of these crosslinking groups has yet to be improved.
Therefore, there is an urgent need for development of new high-performance cross-linkable polymeric electron-transport material.